The energy storage market began to take off when electrical blackouts and brownouts swept the globe, either due to natural disasters or simply because of an unreliable electric grid. The world discovered that storing energy for later use allows modern civilization to balance supply and demand, and maintain electricity during a power outage. Today, the advances in technology from energy companies are increasingly efficient and cost-effective, and are ready to run when the power goes out. When integrated with solar power, energy storage makes the energy of the sun available 24/7.

Annobon Island, the southern-most island of Equatorial Guinea off the coast of west central Africa, is a victim of one of the world’s many unreliable grids. The island has a population of approximately 5,000 residents, with limited access to dependable electricity. In 2014, residents of Annobon Island had access to electricity for about five hours per day, if at all, and even then the electricity did not come cheap as they would spend an average of 15-20 percent of their annual income on supplemental power.

Unfortunately, the scenario on Annobon Island is fairly common throughout the developing world, especially on islands. The quickest and most convenient way to bring electricity to remote areas is with a diesel generator. They are widely available nearly everywhere on the planet, and reasonable cheap to buy and install. The problem comes with the long-term operation of these generators, which can be very expensive, particularly in locations that do not have easy access to the refined diesel fuel that the generators need to run. Furthermore, these generators are loud, polluting, burn significant volumes of fuel, and must be frequently monitored, maintained, and overhauled. Overall, this leads to diesel generators being a very expensive way to generate electricity.

What’s worse, generators are typically oversized for the average amount of power they provide, which makes them run inefficiently, burn more fuel, and need more maintenance. Finally, with many mechanical moving parts they are prone to break-downs and are tough to count on for reliable electricity, especially in warm temperatures.

One new solution to this issue relies on solar energy, advanced batteries, and advanced power electronics and controllers to create a “microgrid” to supply a village or an entire island with reliable and cost-effective electricity. As the technology to do this reliable and cost-effectively has only recently become available, it requires strong leadership and political will to develop microgrid projects at large scale.

Annobon’s President Obiang Nguema had a vision to raise the quality of life for the residents by filling the need for an energy solution that would provide them with electricity for 24 hours a day seven days a week, and after consulting with industry came across solar microgrid technology as an optimal solution. Princeton Power Systems stepped in with the technology and capabilities to prove that one does not have to live on the mainland to enjoy the benefits of affordable, reliable, low-pollution electricity.

Princeton Power Systems, based out of Lawrenceville, New Jersey, opened doors in 2001. The company has extensive experience with microgrids having developed perhaps the highest profile solar microgrid in the world for the US National Park Service on Alcatraz Island in the San Francisco Bay, plus many other projects with customers across the United States, the Caribbean, Europe, and Africa. Princeton’s UL and CE-certified power electronics are used worldwide in advanced battery operations both tied to the electric grid and offgrid, with built-in smart functions for ancillary services.

The company’s project on Alcatraz, off the coast of California, is similar to the Annobon Island situation Princeton Power Systems completed a commercial scale microgrid system on Alcatraz Island, in the San Francisco Bay Area, in 2012. The project on Alcatraz Island continues to be a success and was a winner of the 2014 Intersolar AWARD for Innovative Solar Projects in North America.

Prior to the commissioning of the project, the island’s generators ran on diesel fuel, which created pollution and high carbon emissions in the Bay Area. In 2010, Princeton Power Systems was approached by the National Park Service to supplement these generators with a battery energy storage system and a solar array to reduce diesel usage as much as possible given the physical and budgetary constraints on the island.

The technology involved in the Alcatraz Island Project included a 305 kW PV Array that was placed on the roof of the prison in a flat configuration, rather than angled, to preserve the original island appearance and preclude them from being visible from San Francisco. Multiple Princeton GTIB 100 power control systems, Microgrid Controllers, battery racks, and generators were placed in an old generator room to prevent saltwater damage and out of view of the million visiting tourists each year. The solar array directly powers the island loads, through the GTIB power converter, and any excess generation is stored in the 2 MWh battery. The battery is discharged at night to continue to supporting the island, and when necessary a diesel generator is automatically started to provide additional energy.

The primary purpose of the microgrid is to provide 24/7 reliable energy, with secondary goals of reducing operating costs and emissions that are directly tied to diesel fuel use. The batteries and sophisticated Microgrid Controller alone would reduce diesel fuel use by about 20 to 30 percent, and combined with the solar array the island is running generators up to 80 percent less. When the diesel generators do run, they run on ultra-low sulfur diesel fuel and are powerful enough to meet the island load and charge the batteries.

One important concern of the project was the preservation of natural environment and wildlife of the island. The word “Alcatraz” can be translated into “pelicans” in old Spanish and there was extra attention given to the solar panels after the birds of the island were dropping rocks and shells while flying overhead, and the construction logistics paid very close attention to not disturbing bird habitats, especially during nesting season.

The majority of the island’s power is now produced by solar. The batteries of the system provide additional energy storage for use when the sun is not shining on the PV array. In addition, if the solar and batteries are not available, then the generator kicks in automatically and runs with maximum efficiency to recharge the batteries while simultaneously powering AC loads at this National Park Service site. The system is managed using a frequency-shifting control strategy that requires zero communications among the micro-grid inverters. The National Park Service has reported a net diesel fuel reduction approaching 80% compared to the original generator only power system. They are pleased with the performance and Princeton Power has since done a second system at another National Park Service site on Lake Superior.

Princeton Power Systems took what they learned from the Alcatraz Island Microgrid project to implement Africa’s largest solar microgrid and resolve the lack of reliable electricity problem on Annobon Island. In collaboration with the project developer and partners, Princeton Power Systems began the build-out of a 5-MW self-sufficient solar microgrid on Annobon Island, consisting of 20,000 solar panels split into three geographically-separated arrays, three large-scale advanced battery banks, and redundant generators.

The microgrid is enabled by Princeton Power Systems 250 kW battery integrated inverters (BIGI), twenty of which are installed across the island to condition the power from the solar arrays and batteries, and to manage power flow between the different sources and loads. The BIGI-250 is the world’s first multi-port, DC-coupled power converter designed for cost-effective solar and battery microgrids like the one on Annobon.

The BIGI-250 operates both on-grid and off-grid and features built-in smart functions, such as demand peak shaving, photovoltaic (PV) ramp rate control and area frequency regulation (AFR). It includes a droop control algorithm that allows multiple power converters to synchronize on an AC-microgrid along with diesel generators and without dedicated communication lines between the converters. This control method allows inverters to drop off-line or communications to go down without affecting the reliability of the electric grid.

The control structure is based on Princeton’s Energy Management Operating System (EMOST) and four EMOS-Hub controllers placed around the island. There is one EMOS-Hub located near the mouth of the island’s inactive volcano, another near the island’s airport, one near the island’s only hotel and the fourth master controller near the southern tip to coordinate between all of the locations and support three small villages. The island-wide microgrid EMOS controllers allow remote control and monitoring of the power system, and allows remote maintenance and software upgrades as needed.

The island-wide microgrid on Annobon will provide reliable, predictable power, supply enough electricity to handle 100 percent of the island’s current energy demand, and will be the largest self-sufficient solar project on the continent of Africa. Solar power with advanced batteries provides a cost-effective way to bring electricity to islands and remote areas with much lower emissions than fossil-fuel generators. Modern solar panels are far more efficient and cost-effective than their predecessors, and advanced batteries that can support the daily charging and discharging required for microgrid operation are just now becoming widely commercially available. The electronics and controls required to manage these assets has been demonstrated for several years in projects including the Alcatraz Microgrid.

The Annobon project is a part of Equitorial Guinea’s National Economic Development Plan Horizon 2020, which aims to make Equitorial Guinea an “emerging economy” while accelerating its development and democratization by 2020. Along, with a much needed power supply, the microgrid will enable the development of multiple industries on the island, therefore, providing residents more jobs and significantly raise the standard of living.